1. My family chose homeschooling because my twin sister and I already knew how to read and write when we were the right age for kindergarten. Our parents thought we might be bored in all-day kindergarten. So they decided to wait a year. And then another. And another. Finally, they decided to homeschool us through high school. (now we have a litle brother who is also homeschooled.)
2. Yes, I've heard of it, but it's not something I can see my family ever doing. Personally, I need a schedule to follow.
3. I have lots of friends, most of which are also homeschooled. I belong to two homeschool groups in my area. My two best friends (besides my sister) live around the block, and we met them at a library program.
I don't live in the country; if I did, I probably wouldn't have as many friends as I do. My advice for that is to #1, ask your mom (or whoever teaches you) to find out if there's a homeschool co-op near you, #2, volunteer and participate in as many things as you can.
4. There are ways to get diplomas through homeschooling. There are places (websites, mostly) where you can send in your transcript and they will give you a diploma. Most colleges will accept them, as long as they can also see your transcript (which you and your mom/teacher should start working on as soon as you are in high school, if not before. I don't know how old you are, but I'm assuming you're in high school.)
Let me know though this thread if you have any more questions.